Process of finishing fish skins



Patented Apr. 7, 1953 PROCESS or FINISHING FISH SKINS Henry Rose, Gloversville, N; Y.

No Drawing. Application February 2,

Serial N- 209,211

'3 Claims. (01. 69 21) gether'with a color or dyeing operation and a glazing operation, a smooth, serviceable and uniform product results having a novel two-tone efiect. The process can be effectively employed for the preparation and treatment of the skins of such fish as salmon, Atlantic salmon, steelhead trout, trout species, herring species, halibut, flounder species, cod species, rock fish species, tuna species, and the like.

The present process'will be described immediatelyhereinafter and it will'be evident to those skilled in the art that several of the operations included in the process are conventionally employed for the conversion of fish skins to leather. The skins are soaked in water overnight and washed out salt-free with water at room temperature, or approximately 70 F., after which the skins are fleshed, either manually or mechanically, and again washed for approximately fifteen minuteswith water maintained at a temperature of approximately 45-75 F. Thereafter, the skins are subjected to a swelling-operation which removes most of the scales. Any alkali, such as sodium'or potassium hydroxide, 'or lime, or sodium sulphide, can be employed, alone or in vari ous combinations, in a solution containing 0.5 to 1.0% by weight of the alkali, the skins remaining in this solution from one to three days, it being preferred that the alkali be present in an amount of 2.0 to 10.0% by weight of the skins treated. Thereafter, the skins are washed thoroughly for two to three hours until the swelling is completely removed. The abovedescribed soaking, 'fleshing,:and swelling operation is conventional in thear't. Inasmuch as these operations fail to completely remove the scales from the skin, the skins are brushed or otherwise mechanically or manually treated to remove theremainder of the scales.

After'the completeremoval of the scales from the skins; the skins are "again washed with .water and subjected to bating in the presence of pancreatic enzyme. Depending upon the kind of leather desired, the bating can be carried on from one to twelve hours, the longer the treatment, the softer the leather. An aqueous solution of the pancreatic enzyme is employed in concentrations of 0.25 to 0.50% by weight, the temperature of the solution being maintained at approximately 45 to 70 F. and at a pH of 8.5 to 9.0.

The conventional procedure in the treatment of the fish skins after bating is to split the skin with some of the scales thereon, but it has been found that such splitting causes-unevenness in the structure of the skin, is very dimcult to control, and results in the loss of a large percentage of the leather. The present process has been provided to overcome disadvantages of the splitting operation as will appear hereinafter.

. After the bating operation, the skins are again washed with water and are subjected to a tanning operation. The tanning is carried out inthe presence of aqueous vegetable extracts, such as anextract of the quebracho bark or the extract of the sumac leaves, or may be carried out in thepresence of a synthetic material such as syntan, a condensation product of coal derivatives, suchas a-condensation product of naphthalene sulfonic acid and formaldehyde. The skins are maintained in the extracts for approximately two to three days or until complete penetration takes place, the extract being employed in an amount ranging from 10 to 70% onthe basis of the drain Weight of the skins. It is preferred that theskins be;maintained in the extracton the 10% level, first, the extractincreasing every two hours until to has been added; 7

1 At this stage, before vegetable tanning, th skins can be bleached, if desired, in the following Way. a The skins are immersed in an aqueous solution of potassium permanganate for one-half hour or until the skins have a uniform reddish color. Potassium permanganate isemployed in an amount equivalentto 0.25 to 1.0% by weight of the drained skins. After the skins are washed and rinsed to remove the excess permanganate, they are treatedwith an aqueous solution of bisulphite, such as sodium or potassium bisulphite, or any other water soluble bisulphite, until the skins are substantially white and all pigmentation has disappeared. The bisulphite'is employed injconcentrations: equivalent to 2.0 to 3;0%Ib weightof the drained. fish. skins. Aftenth bleached skins have been washed .free of bsulphite'theyiare-subjectedito the vegetable tan-i ning' 'idescribedtimmediately, hereinabove; It

should be remembered that various kinds of bleaching agents may be employed instead of the bisulphites, such as the peroxides in the presence of ammonia.

The bleaching operation can be carried out in still another manner. The skins may be run into a solution of B. sodium chloride and 1.0 to 2.0% sulphuric acid on the basisof the drain weight ofthe skins. Thereafter 1.0 to 3.0% by weight of potassium permanganate is added and after approximately one-half hour 2.0 to 3.0%

by weight of the bisulphite is added until the skins are completely bleached. The: skins. are

then drained and a 6 B. salt solution is added in sufiicient quantities to cover the skins. This bleaching operation can be immediately-followed with a vegetable tanning operation in which a' 20.0 to 30.0% by weight of quebracho or other vegetable extract may be-added to the salt solution and the skins maintained in this combined salt and vegetable extract solution for approximately one hour, after which another 20.0 by weight of the extract is added and the skins are left in this solution until complete penetration of the skin occurs. After the penetration, the skins are washed out salt-free and are thenreadyfor the fat-liquoring process.

If desired, the tanning of the fish skins may be carried out after the pickling and bleaching operation by-a process-conventionally known as chrome tanning. In this process, the skins-after pickling, are's'ubj'ec'ted to an aqueous solution-of chromium sulphate employed in an amount approximately of 10.0% by weight of the drained skins. After twohours of treatment with the chromium sulphate, sodium bicarbonate is added until the pH is 4.6 and the skins are leftte soak overnight. They should stand the boil test of 180490 F; and are washed out at approximatel'y' 100 F. for approximately one-half hour and neutralized with sodium bicarbonate until the pH 'is 5.5. Theskinsare then treated with 10% by weight of a vegetable extract, such as quebrach'o or sumac, after which the skins are'ready for fat-liquoring. Any combination of known tannages may be applied for fish skins; like formaldehyde-or formaldehyde and chrome combinations, and the like.

After the skins. are vegetable-tanned as in any of'theabove processes,- they are fat-liquored with 2.0 to 4.0% by weight of sulphonated cod oil' (medium sulphonation), at a temperature'ofap proximately 110 to 120 F. for approximately forty-five minutes. The skins are then hung up to dry-and if they are crusted, after drying, they may be resoaked. After fat-liquoring the skins, they can be colored with any suitable dye such as 1.0% by weight of Acid Anthracene Red GA Ex. Gone. and Brilliant Croceine 3 BA at a temperatureof approximately 100 F. The dyestuff is exhausted with a 0.5% formic acid and pasted. After the skins are pasted and dried out, they arestaked and buffed on the flesh side.

At this stage, the skins are subjected to a burning or singeing operation which constitutes the heart of the present invention. This operation, in effect, burns off the tips of the scale pockets: without burning or otherwise affecting the-remainder of the skin so' that a smooth anduniform. fish skin results which has a unique and exceptionally attractive. appearance. The pockets-in which the. scales are embedded are quite: uniform in character, but they have a very thirr layerof. kollagen at the end of the pocket, which. makes the appearance non-uniform.

During the process, the ends of the pockets become muggy and partly decomposed. Since, as pointed out hereinabove, splitting or any other operation like buffing produces non-uniform effects, the present burning or high temperature treatment produces the uniformity and attractive appearance desired and also improves the serviceability of the skins. The skins may be subjected to high temperatures,,,.in' thexorderi of 800 0., using an electric plate, rollers, or at gas flame. The preferred operation is carried out by having a hot flame close to the surface of the skin, the. skins being. folded on a pipe thru which cold water is flowing, so that the high temperature of the flame will affect only the tips of the scale pockets and will not scorch the skins. Before theburning operation, it is advisable to brush the skin against the scales so that the pockets will stand out, it being understood that the burning will be more easily accomplished in some speciesv of this skin, in which case the brushing will be. unnecessary. Although the temperature of the burning. or singeing. isapproximately 800"" 0., it should be understood that heavier skins; can tolerate more burning at. somewhat. higher temperatures, whereas the lighter skins will have to be adjustedaccordingly. Electric rollers may be employed instead of a direct. flame and bothmeans may beemployed to obtain different. fife"- fects on the product. This burning. operation. can also be applied to any reptile skins, like. snakes, e. g.,v boas, pythons,, etc., in a similar manner.

And .finally, the. skins: are brushed, glazed and plated, preferably under a-Sheridan plating'machine'at a temperaure'. of approximately 200 F. The brushing and glazing may be repeated as desired and after the glazing, it will beseen-that a very attractive two-tone effect is obtained. In the event that the. skins are not colored after the vegetable tanningv process, the skins can be table-colored, using acid or basic dyes, by-swabbing the colors on the skins,-.and after the skins. aredry they can be subjected to the burning or singeing operation described immediately hereinabove. After the vegetable orchrometanning, if desired, the skins can be. shaved on a shaving machine, in which case the-staking and" buffing may be omitted. It will also be understood that a machine arrangement can be employed for the singeing or burning and brushing operation as well as. a hand-operated. blow torch.

The following examples will illustrate several ways in which the present process. has been carried. out.

Example I One hundred fish skins were soaked in. water at room temperature of approximately 70 overnight, and on the second day washed salt-free with water at a temperature of 45 to 70 F. and then fleshed. The skins were subjected toa swelling. operation to remove a portion of the scales by washing at 45 to 70 F. for one-half hourrin a solution: containing 50 gallons of. water and 2.50 lbs. of soda ash, and the skins were allowed to remain in this. alkali solution. overnight. The skins wereth'en washed for approximately one-half hour with water at. av temperature of approximately F. and. then subjected. to the bating operation. employing. 50 gallons of waterand: 210 lbs. of Oropon A. The bating is followed with a. tanning operationin which the skins are first washed with water at approximately 70 for one-half hour and then soaked in a solution for one-half hour containing 25 gallons of water, 2.0 lbs. sumac, and 1.0 lb. syntan. 2.0 lbs. more of sumac is added within an hour and the skins are left to soak overnight. On the next day, another 2.0 lbs. of sumac is added over a period of two hours and the skins are allowed to soak overnight. The skins are then shaved and washed for onehalf hour with water at approximately 120 F. and then washed for one-half hour with a detergent solution at approximately 120 F. containing gallons of water and 1.0 lb. sulphonated cod oil. The skins are then pasted, staked, buffed, burned or singed, brushed, glazed and plated in the manner described hereinabove.

Ewample II In this example, 100 fish skins are treated to a soaking, fleshing and bating operation in a manner which diifers from that described in Example I. However, the tanning, singeing and other operations as described in Example I remain the same. The fish skins are washed with water salt-free and are fleshed and washed cold at a temperature of 45 to 70 F. in ten minutes. The skins are then immersed in an aqueous solution of sodium sulphide in an amount of 2.0% by weight of the fish skins. The skins are then washed with water at a temperature of approximately 70 F. and then subjected to a solution for one-half hour of gallons of water and 0.5 lbs. of sodium bicarbonate. The skins are again washed with water and unscaled either by hand or by machine and then again washed with water for twenty minutes at a temperature of approxi- 6 mately F. The skins are then bated for two hours in a solution containing twenty gallons of water and 1.0 lb. O-ropon A. After appropriate washing of the bated skins, they are tanned and otherwise treated as set forth in Example 1.

While a preferred embodiment of the invention has been described hereinabove, it will be understood that minor variations may be made in the process without departing from the spirit of the invention and the scope of the appended claims.

Having described the process, what is claimed as new is:

l. A process for treating a fleshed, descaled, bated, tanned and fat liquored fish skin which consists of the step of burning off the tips of the scale pockets without burning the remainder of the skin.

2. The process of claim 1 wherein the burning is carried out at approximately 800 C.

3. The process of claim 1 and the step of glazing and plating the skin after the burning operation.

HENRY ROSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,230,266 Bendixen June 19, 1917 2,181,243 MacDonald Nov. 28, 1939 2,222,656 Erkel Nov. 26, 1940 2,272,935 Cotton Feb. 10, 1942 

